This is a psychophysical investigation of the mechanisms involved in the perception of spatial patterns by normal, human viewers. The results of recording from single cells in the visual system and the results of recent psychophysical experiments have led to a widely entertained model of pattern vision, often called the multiple-tuned-channel model. The research elaborates the model by pursuing two major questions. First, to what extent is the information (spatial frequency components, contours, etc.) presented at one orientation within the visual scene processed independently of information presented at other orientations? Second, is there inhibition between channels tuned to different features? For example, is there inhibition between channels tuned to different spatial frequencies or between channels tuned to lines and channels tuned to edges? If there is inhibition, what is its character and possible function? Adult subjects with normal vision are used. Stimuli are viewed centrally at photopic luminances. Detection and recognition tasks are used.